Ingress, Google's science-fiction-ish, location-based, augmented-reality-style game for Android, became publicly available on Dec. 17. Ingress is not a game that your friends can easily explain to you, if they're even playing it. Nor is it a game that any two people might "play" the same way. That's in large part because you don't really "play" Ingress. Allow me to explain.

I have been playing Ingress since a week or two after the private beta opened up in October 2012, loosely joined up with a local Ingress community, and introduced a few people to the game. I see and receive questions like:

What's the point, exactly?

Where do I start?

What do I do if there are no Portals anywhere?

Am I supposed to play this while driving around?

Good questions! But you may have other questions, which I will try to anticipate here. I want you to play Ingress, if you might enjoy being a key operative in a big pretend magic-energy army. You probably know if that's your thing or not. Here is everything else you want to know before starting.

I just installed the game and launched it. Should I join "The Englightened" or "The Resistance?"

It doesn't really matter, overall—neither faction has particular special powers of note, especially at the beginning stages. You might ask some of your friends if they're playing for either side, or enter your home or work ZIP code in the Ingress Intel Map and see if one side is dominant in your area. And that shouldn't sway you, either; it can be very fun, and advantageous, to be an Enlightened (green) agent inside a swath of land controlled by The Resistance (blue).

What's this game about?

Let me try and explain this weird thing in one paragraph:

The goal is to help one of the two worldwide forces to capture and keep control of key points and large areas, on a real map that looks like a sci-fi version of an actual Google Map. You do this by attacking Portals you find out in the areas you travel around, and also by setting up your own Portals and boosting those that others have set up. It's really nerdy, but it's also a good excuse to take a walk, walk the dog further, and compete with your friends.

I've signed in, and there's a map, and ... what am I trying to do?

The early learning curve is a bit tough on Ingress. For at least a week, I was not quite sure what the "Hack Portal" action really did, or whether I was supposed to use it on just enemy Portals, or my own side's Portals, too.

So here's the deal, the basic gist: your side is trying to control as much of the area around you as possible. In the game's story, you are trying to control minds in your area and either advance or keep away a mysterious extra-dimensional energy, but in day-to-day playing, you are simply warring to control an area.

You start by capturing and maintaining a Portal. You find Portals by opening up Ingress while you're walking around, or perhaps on trains or buses, and surveying the map around you, looking for glowing points of energy. Or simply scan the Intel map on your desktop browser

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Do not open Ingress while you're actively driving, because believe me, you are never going to get paid for this. Portals are most often located at public points of interest: statues, historic markers, buildings of some note, libraries, public artwork, places like that. In fact, it's a requirement that a Portal be a publicly accessible spot that can be reached at nearly any time. Portals are, like many things, more concentrated and easily found in cities and densely populated areas.

Okay, I found a Portal. Now what?

Most likely the Portal is already claimed by a faction: blue for Resistance, green for Enlightenment. What you should do—what you should always do—-is hack the Portal. "Hack" implies an attack to most people, but think of it more as "tapping" the portal.

Hacking the Portal will probably give you a few things, depending on the "level" of the Portal and other conditions:

"XMP Bursters," which are weapons you can use to attack enemy Portals (even the one you just hacked). They come in different levels, 1-8, with eight being the strongest.

"Resonators," which you attach to Portals in sets of 8 in order to claim them (and which you attack with XMP Bursters). Like "bursters," they have a levels of 1-8, with 8 being the most hard to destroy.

A "Portal Key," which allows you to remotely recharge a Portal, or link it to another portal to eventually create a three-Portal "Control Field." You lose (burn) a Portal Key every time you link that Portal.

Portal modifications, like Shields, a Link or Force Amplifier, an attacking Turret, and helpful improvements like Heat Sinks and Multi-Hacks.

"Media," in the form of notes and videos, that you can view to glimpse the cryptic story behind Ingress.

How do I actually attack or hack or claim portals?

Everything is based on touching things on the map. Press and hold down on your location to bring up a menu for attacking and submitting new Portals. Tap on a Portal to bring up actions you can do with it.

What determines what kinds of stuff I get from Portals?

Generally, it's the level of the Portal itself. A Portal's level is determined by a weighted average of the Resonators attached to it. If you hack a level 4 Portal, you will likely get Resonators at level 3, 4, or 5. Exactly what you get is also based on how often you have hacked that Portal, and other unknown factors that Google balances (kind of like their search engine!).

I've hacked a Portal, I got some stuff. But that's not it, right?

No sir. At first, you should indeed spend some time hacking different Portals and exploring the layout around the places you go. But eventually, it will be time to start attacking, capturing, and reinforcing Portals.

The crummy part, though, is that you can only use weapons and Resonators as high as you have leveled up. That makes the early stages of the game rather difficult. At first, you can't even use any of the level 1 Bursters (weapons) that you get from the weakest of Portals. So you go around hacking and wandering.

But you'll eventually acquire enough "Action Points" (basically "experience points" in any other game) to level up to level 1, and then you can start attacking other Portals (weakly), adding and upgrading Resonators to Portals your side controls (weakly), and maybe even linking Portals to one another.

At first, when you are at lower levels, Ingress is heavily weighed toward building up Portals, rather than attacking. You can't make much headway against a level 6 Portal that has Shields with your level 1 weapons, but you can claim new Portals for your side, link Portals together, and, in particular, link Portals in triangular sets to create fields, worth 1,250 Action Points just for setting up. Once you're somewhere above level 1, you can start attacking Portals, breaking Resonators, and even reclaiming a Portal for your side, which gives you huge Action Point bonuses.

XM is that other-worldly energy mentioned earlier. It's all those little blue-white dots you see as you wander around in Ingress. Portals often have a lot nearby, and they recharge frequently. You need XM to fire Bursters, hack enemy Portals, and do most actions in the game. You shouldn't run out too often, except when you're really on an attacking spree.

I hardly see any Portals at all where I am. How can I get anywhere?

Other than traveling, your goal then is to submit new Portals in the game. Find something around you that might be a notable spot that people notice, then, in Ingress, press and hold on that location and choose "New Portal." You'll be guided through taking a picture of that thing, describing it a bit, and submitting it for review by the Ingress team. It's definitely not an overnight process, but I've added two Portals to my area. Which I no longer control, but nonetheless.

Why are we doing this? What does Google get from this?

Why are you doing it? Because you want something to do with your phone for even more moments of your day. And because it is fun to join up with a team, scheme to defeat the other team, and walk past your local library or a downtown statue and think to yourself, "I own that. I liberated that from the other side when they had let their Resonators down."

Why is Google doing it? Their response, so far, has been along the lines of trying out a new kind of mobile game, with a small in-house studio. Most people looking at this game, though, believe that Google is gaining important knowledge about walking times, areas of public spaces that cars cannot reach, and lots of public photos of important, visible things. That has to be valuable to a company whose stated goal is organizing the world's information.

Is there an endgame?

Not so far. Players are currently capped at Level 8, and the maker says that missions are coming soon, but right now, you're locked in an eternal, endless war with minor victories and retreats between factions. It is, in some ways, almost too realistic.